If the guy tells you just let me put the 'tip' in is that bad?

It means that he isn't serious, so don't trust him.

If you want to have sex, then go ahead and do it - all the way. And if you don't want to have sex, then don't trust him to put "just the tip" into your vagina. You can get pregnant that way, he probably won't be able to stop himself, and you'll both feel miserable about it.