If the active ingredient is aciclovir, then it's a bit of a problem, because it interferes with DNA replication. You've probably not had a big enough dose to be an issue, but maybe lock the tube away for a while.

I only know about it because a chemist warned me that I shouldn't use it while pregnant. I wasn't pregnant; just a big lunch! But maybe he was just being super diligent. Wish more pharmacists were!