My three year old boy hit the back of his head against the centre table and the place swole up. He hit the same place on the same table and it swole up even further. A nurse placed him on Ibuprofen. However this morning, I noticed that the place was emitting pus. I pressed out the pus lightly and the lump went down a bit although I still feel that more pus or contaminated blood would have come out if I had the mind to press harder. What should I do ?