The TB Test should be a formality. It's showing the funds and the credibility interview that will be the defining factors in your Student visa application.

You've also got to plan ahead as to how you're going to get funds out of Nigeria. Right now, I bet whichever Uni you are going to seems lovely and supportive. Wait until you try explaining to them what a 'Form A' is and why it takes months to get the money to cover your costs of study into the UK. See how supportive they are then...