I had nerve conduction studies done, due to tingling numb ring and pinky fingers. What is an ulnar lesion at elbow please? And is it permanent?

Ulnar neuropathy. Ulnar neuropathy is a nerve problem affecting the ulnar nerve at the elbow, typically caused by compression, entrapment, or trauma. It is the second most commonly pinched nerve in the body (after carpal tunnel in the wrist). It is treatable with strategies to protect the nerve (avoid prolonged elbow bend, pressure on elbow), therapy, a splint or brace, and surgery.
Not usually perm. "lesion" can mean many things-in this case, it refers to the location of what is causing your problem. The ulnar nerve has several functions with one being sensation to the 4th and 5th fingers. So numbness and tingling suggests the ulnar nerve is irritated, confirmed by the emg. Most common is from pressure at the "funny bone" where the ulnar nerve travels.Often stopping pressure cures it.
Nerve compression. It sounds like you have compression of the ulnar nerve as it crosses the elbow, which is extremely common. It often improves with limiting compression at the elbow, most commonly with some combination of change in habits, elbow pads, physical therapy, injection of steroids, or surgery to move the nerve out of the way.