This is Dr. David
I am sorry you have been having such bad nasal congestion.
you can try over the counter allergy medications like benadryl (diphenhydramine) or allegra (fexofenadine)
and nasal steroid sprays like nasonex (mometasone) or flonase (fluticasone)
you really should consult an ENT doctor specialist.
you might require a sinus surgery to open up your sinuses and help with sinus drainage
I know it can be hard to see a doctor in nigeria.
here is one list
let me know if you have questions.