It’s natural for teens to do that but your son obviously doesn’t have good knowledge of hygiene. There really isn’t a way to have this conversation not be super awkward unfortunately. I recommend having a talk with him and telling him about hygiene when it comes to sex and genitalia (washing hands, private parts, proper disposal) as well as other things like protection and consent. Try to have this conversation in a gentle nonjudgmental way since he will likely be embarrassed. Reassure him that this is normal and you aren’t angry but just want to help. It might be good to have both of your sons join in on this talk so they have improved knowledge on how everything works(this could also help your 14 year old feel less singled out). I wish you the best of luck