You can now buy bitcoins in Nigeria using your PayPal account. This can be done on Bitkonga Exchange site.
The benefit of using this method to buy bitcoins is because it is cheap. Bitcoins will be bought using official exchange rate which is not available in the market majorly due to Nigerian government restrictions on foreign exchange.
The limitation to this method is that you are only allowed a monthly Limit of $100 spend according to Nigeria government rules.