Suggest Treatment For Lump On The Back

hi my son had a small lump on his back like a cyst - it was nothurting andwhen you touched it it sort of moved around. He is 23 years ol d. yesterday we decided that I should prickit with a needle maybe it will flaten out and if there is any pusit will come out - (stupid of me) I did it and sterilised all needle etc. blood and water came out nothing else andtoday its hurting him when he touches it. I went to the chemist and got him some antiseptic cream to put on it. What else can I do? It is a bit red and swelled a bit but nothing major as yet. The cream is called betadine tku carmen