<s>[INST] Hi my boyfriend had this knot located on the back of his head, he fell from a tree when he was a kid he mashed the knot one day and this pussie white stuff came out of out and it had the worse odor he was scratching his head today and he noticed the knot or lump still had the white stuff coming out [/INST] HiWelcome to hcm.First thing is that it has nothing to do with fall in childhood. Mostly it it Is a sebaceous cyst which requires complete excision surgically. Incomplete removal by pressing it will cause recurrence. So see your surgeon for it's removal. It is not very serious problem so don't worry.Regards </s>