My son of 17 years still can retract his foreskin fully. do we need to seek medical attention or will it sort itself over time?

Do you mean he can't fully retract his foreskin? If he can't, there are exercises he can try which may help & could avoid circumcision. . It's best to get the advice of a urologist,however.

One way to correct that is to retract a well lubricated foreskin a little bit more every day till it easily retracted over a period of time. make sure not to leave the foreskin back when done. Faster way is circumcision