If you are looking for medical advice for your son, these forums are not the place to get it. What you need is a diagnosis, first of all to determine if there actually is a problem and, if so, what the optimum solution might be. Ask your doctor for a referral to a paediatric urologist and go with your son and your partner.
As a general note, trying to retract a 4yo's foreskin, with or without "creams", is more often a source of problem rather than a solution. But no-one here can know about the specifics of any particular situation -- that's why we have specialists, and why specialists start by doing an examination.