A Tourist entry permit

Yes, yo need it. You can apply for it through the HK Immigration Department directly or through the Chinese embassy in Nigeria. The application documents needed are:
Application for Entry for Visit/Transit (ID 1003A)
Your personal recent photograph
Photocopy of your passport
Photocopy of your financial standing proof, e.g. bank statements, savings accounts passbooks, tax receipts, etc. and proof of employment (if any), e.g. company leave letter, salary slips, etc.
Photocopy of proof of transportation arrangement, e.g. flight itinerary
Photocopy of proof of the proposed leisure visit to Hong Kong, e.g. receipt of joining a package tour to Hong Kong, itinerary, etc.