First, did you see a physician to get the diagnosis and did you get an imaging done? Did the doctor say whether the symptoms were from an inflammation of/around the ulnar nerve, impingement of the ulnar nerve due to restricted musculature and ROM, or if there was an anatomical issue (smaller ulnar groove, laxity or tearing of the fascial sheath covering the ulna, etc)?
How you approach your rehab will vary depending on your specific situation, but a generalized answer would include 1) improving soft tissue quality and maintain appropriate tissue length of the wrist flexor/pronator and extensor/supinator masses, biceps and triceps; 2) continue to strengthen and train the surrounding musculature for stability of the elbow and quality movement patterns; 3) some anti-inflammatories may help relieve some of the "pressure" in the area.
I would avoid excessive hypertrophy of the flexor mass, especially if the symptoms are caused by the ulnar nerve being pinched by the surrounding musculature.
In the end, the surgery isn't horrible if it comes to it, but as you stated is not completely necessary unless the symptoms are not resolving or they become too great to handle.