Suggest Treatment For Pus Filled Bump On The Arm

I had a rather large bump on my arm so i squeezed it and some puss came out. Today I looked at it to see if it had gone away and noticed that the top had dried with a yellowish color with a black tip. so I picked it off. Then some sort of yellow puss came out and it bled a little. When I wiped the blood away there was a small hole and blood was accumulating in it. Is this normal?