How to get rid of medical glue?

My now 18 month old son had a deep scratch on his head almost 4 months ago and we took him to urgent care where he got it glued together. They told us it would fall off on it's own in a week but here we are lol. It's still glued down with his hair like it was 4 months ago- not loosening up at all and we are really worried about what it's like under the glue - if he's going to have a bald spot etc. Does anyone know how to get rid of it? Our pediatrician had no advice for us.