Spot under my lip which has gone worse?

Got up one morning and my lip was sore and just under the lip above my chin there was a small spot with a black head on it. I burst that (I know I shouldn't have) now it's gone worse my lip is bruised and the spot has became big and has yellow stuff in it. It burst itself but then it comes back itself. Any idea what it is? So far been taking pain killers as it's very painfull