worry about what...you think he's too big?? With a little persistence and patience...and a lot of lube...it will fit. AND if you break up and your worried about whether your pussy will tighten back up for the next guy...yes, it will tighten back up. Ever hear of Kegels?? Look into it. Then you'll never worry again. It makes it your pussy [or ass] snap right back into place, just like a Venus Fly Trap. So the next guy will never know the difference, and the current guy will think you've got the best pussy in the whole world.
P.S. If you didn't already know. The average penis size is 15.5 cm long and 12.7 cm thick (circumference). [6" x 5"].