There's nothing you can do about it except go slow and try other things first to get a sense of each other's comfort zones.

Don't worry you have to keeep on using your finger frequently and slowly with your penis

i agree you are VERY young to be having sex...are you well aware of ALL consequences? are you prepared with condoms? you need to think about all of this before having sex...also like the others said, just make sure to take it real slow, usually the first time isn't always the best..it takes a while to figure out what you like..so just make sure you're both comfortable and REALLY ready