I've done some research on the subject, i hope you have too.

From what i've gathered, if it is infact a tumor, it's far more than likely not your fault, having to do with genetic cell growth. I typed 'newborn lump head' into a google search bar, and went from there. If you've already done such investigations, then you're just loooking for someone to tell you that it's not your fault. In regards to such a serious circumstance, you'll most likely have much better luck talking to physicians. Drugs and alcohol probably cause deffects we're not even aware of yet. I smoked pot during most of my pregnancy and my son is perfect, whilst others have said they had 1 joint or 1 cigarette and their child was born with asthma. And you're saying you did both and drank.

It's too late to change this, regardless of what it is, and what happens, i hope at the very least you have learned from this. I hope 'the girl and her baby' the absolute best. All you can do now is accept things the way they are and love your baby to no end.