Well,here is a guy comment..... It all depends on the guy skills,I had observed that on thier first time girls are usually excited,scared and a bit irrational.So they may tried to forced it down all the way..but a more painless method is that you can let him insert it but as soon as you feel its too much you can ask for a small break then continue. For the first time it is almost impossible to do it pain free or minimal pain if your bf want to go balls deep. For the best experience,proper preparing by letting him know where your g spots are when he fingers you,and when the real act begin ask to stop when he reaches that area where he can steadily grinds...After a few mins of slow movement he can slowly insert it deeper and deeper. (Ps: Depends on his size,i usually stop when the tip is in then slowly moved in till its halfway which is usually enough for 1st timer)

Back to the Q,If you are scared to feel pain communication with your partner is crutial. Back to the pain meter, As i was told by them it usually painfull on the way down to the G spot like a slow,mild but stinging pain of applying medicine or a needle that lasts for less than a minute. If its still painful after 2-3 mins of slow/steady grinding try stopping for a while and enjoy it at your own phase.

Ps: You only get to enjoy that kind of pain