As a Nigerian you are free to walk in to any Nigerian Immigration center and get your passport.
General Documents that is expected from you are:

Recent color passport photographs
Birth certificate or age declaration.
Local Government letter of identification.
Guarantor's form sworn to before a commissioner of Oaths / Magistrate / High Court Judge (optional)
Consent letter from parent for minors less than 16 years
Marriage certificate if married


The Following Tables list Passport Application Fees by Age and Booklet type.


APPLYING IN NIGERIA FEE (NAIRA)

Number of Booklet Type AGE 0 - 17 AGE 18 - 59 AGE 60 and above
32 Pages 8,750 15,000 8,750


64 Pages 20,000 20,000 20,000

PASSPORT FEE - ALL EMBASSIES (US DOLLAR)

Number of Booklet Type AGE 0 - 17 AGE 18 - 59 AGE 60 and above
32 Pages 65 94 65


64 Pages 125 125 125


For the benefit of our readers, there are 44 countries in the world today that Nigerians can visit. Below are list of countries that Nigeria citizens can easily come in without the stress of acquiring a visa, though there are few numbers of counties you are expected to pay a token fee to get Visa on arrival.



Visa-Free Countries:

Benin Republic (Visa free)
Barbados (Visa free for 6 months)
Burkina Faso (Visa free)
Cameroon (Visa free)
Chad (Visa free)
Cote d’Ivoire (Visa free)
Dominican (Visa free for 21 days)
Fiji Island (Visa free for 4 months)
Gambia (Visa free for 90 days)
Ghana (Visa free)
Guinea (Visa free)
Guinea Bissau (Visa free for 90 days)
Haiti (Visa free for 90 days)
Liberia (Visa free)
Mali (Visa free)
Micronesia (Visa free for 30 days)
Niger Republic (Visa free)
Senegal ( Visa free )
Sierra Leone (Visa free)
Sri Lanka (Electronic travel authorisation)
Togo (Visa free)
Vanuatu (Visa free for 30 days)

Visa on Arrival Bellow

Bangladesh (Visa on arrival)
Burundi (Visa on arrival for 30 days)
Cape Verde (Visa on arrival)
Comoros Island (Visa on arrival)
Djibouti (Visa on arrival)
Georgia (Visa on arrival)
Iran (Visa on arrival)
Kenya (Visa on arrival for 90 days)
Madagascar (Visa on arrival for 90 days)
Maldives (Visa on arrival for 30 days)
Mauritania (Visa on arrival)
Mauritius (Visa free for 90 days)
Mozambique (Visa on arrival for 30 days)
Nauru (Visa on arrival)
Palau (Visa on arrival for 30 days )
Samoa (Visa on arrival for 60 days )
Seychelles (Visa on arrival for 30 days)
Somalia (Visa on arrival)
Tanzania (Visa on arrival)
Timor-Leste (Visa on arrival for 30 days)
Uganda (Visa on arrival)
Tuvalu (Visa on arrival for 30 days)
Source:http://www.karisastravel.com/2016/12/travel-to-44-countries-without-visa-as.html