What Causes Irritation On Tip Of Penis?

Hi I'm a 17 year old male. Recently (past 2 weeks or so) I've had some irritation in the meatus of my penis from it rubbing against the inside of my boxers. Upon further inspection I noticed that the hole appears to be getting bigger, as if splitting downwards. I'm a heavy masturbator, and I've been taking Isotretinoin for acne which has made my skin exceptionally dry. I was wondering if this could be the cause of the split? Is there any way to prevent it from splitting further and return it to its original size? I'm very concerned, but I'd rather not go see a doctor as it's very embarrassing. Could you please help? Are there any creams, or ointments, or anything that I could use? Would Vaseline or Sudocrem help? PLease please please help! Thank you so much!