Visas and vaccinations: All travelers must present the International Certificate of Vaccination against yellow fever, if they are coming from countries defined by PAHO/WHO as having active transmission and at this time:

• Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Panama, Paraguay, Peru, Venezuela and from the African Continent, all countries, Tanzania, Sao Tome and Principe and Somalia.

You need a type "C" visa. This category of visa is granted by the General Directorate of Migration and Foreigners of Nicaragua, the requirements for the granting of the visa, must be presented by the foreign citizen before the Diplomatic and / or Consular Representation of Nicaragua abroad.

• If you have a U.S. visa you will not need a visa to enter Nicaragua. 

Visa application requirements:

This category of visa is granted by the General Directorate of Migration and Foreigners of Nicaragua, the requirements for the granting of the visa must be presented by the foreign citizen before the Diplomatic and/or Consular Representation of Nicaragua abroad.

1. Photocopy of the passport with a minimum validity of 6 months.
2. Letter of request of visa. Original
3. Certificate of criminal or police record of the country of origin or residence, otherwise, Certificate of Interpol Nicaragua. Original.
4. Notarized support commitment of the applicant Original.

Additional: 

When there is no Nicaraguan representation abroad and for the interest of the State the entry of foreigners included in Category "C" is required, the General Directorate of Migration and Aliens, will notify in writing to the Airline authorization of entry of these without Consular Visa, so that the transport companies let them board in the country of origin or residence, once they arrive in the country, they will be authorized entry with Border Visa, having to comply with the established requirements.

• The letter of request for visa must be motivated before the Diplomatic or Consular Representation. In Nicaragua it shall be addressed to the general director of the General Directorate of Migration and Alien Affairs.
• In the notarized maintenance commitment the applicant is obliged to cover the expenses of the foreigner during his stay and return to his country of origin or residence.
• After notification of the Visa of Entry to the Consular Representations the interested party will have 6 months to make use of it, otherwise it will be without effect.

More details here.

Documents to present: 

1. Visa in stamped in the valid passport with minimum of six (6) months.
2. Complete vaccination schedule against COVID-19, those who do not comply with the complete vaccination schedule must present a negative result of RT-PCR for COVID-19, performed within a period not exceeding 72 hours, prior to entry into the country.
3. Vaccination card against yellow fever, in case of coming from a country at risk (mentioned above).
4. Economic solvency.
5. At the entrance to the country, to cancel tourism tariffs, according to the General Law of Tourism (tourism card of 10 dollars Attention: To have the $10.00 in cash, since the migratory authorities do not accept any other form of payment), aquí.
6. Complete the "Entry Request" form. This requirement is for all foreigners entering Nicaragua by air, sea or land. The form must be filled out and sent to the following e-mail address: solicitudes@migob.gob.ni . It is recommended to send the application with as much time as possible. Once the application is resolved, the corresponding Border Post(s) and the applicant(s) will be notified. You can also download the form here.
7. Any other requirements that you are required to present at the time of entry into the country and that are presented at the time of your visa application.
8. It is at the discretion of the immigration authority the number of days to be granted for your stay in the country.
9. Children under 03 years of age are exempted from this requirement, i.e. they will not be asked to enter the country or vaccination schedule or PCR test. These requirements are only indispensable for travelers over 03 years of age. More details here.

Other details, here.

More information details, here.