Talk to Pediatrician on My Toddler Growth

My son is 3 years old and i am worried about his penis size its too small just like a button. I ignored it first because he has just been potty trained just for the day time he still needs diaper during night so i thought the size will get better when he will br potty trained but there is no difference and the problem is that i cannot change his diaper in a public place cuz people wud asking why its too small even if they dont say anything they would just krep staring but anyways pls tell me if i need to go and get him checked by a doctor cuz some people have started saying so please help me what to do