Damaged nerve in leg due to shots

My male cat, Pooper, will be 2 years old in July. 3 weeks ago I took him for his shots and he had a bad reaction. He was given 2 more shots in his right hind leg. When I took him home, he was having a horrible time walking. I called the vet and was told this was normal. It didn't change much so, I took him back 5 days later and the vet then informed me that he had nicked a nerve. He assured me it would heal and would take a month or so. Yesterday, my boyfriend took him for a cortizone shot to help with the healing process. The vet then informed my boyfriend that it may not heal and that it could be permanent.
He is still jumping but, doesn't run much. His favorite bed is 5ft off of the ground. He doesn't seem to be in pain but, cats do mask pain very well.

Does anyone have any advice for help in the healing process??

An update: Even though no one had any advice, we waited it out and it took almost 2 months to see progress. One of the things the Vet told us was that it would take upwards of a month or more to heal. He told me at the 5th week that he was permanently damaged and would never heal. He was wrong and it turns out that for nerve damage it may even take as long as 6 months.

Another issue we had was the cortizone shot. For weeks, Pooper was lethargic and tired. I had to call the vet to find out that cortizone lasts 6+ weeks and those are side effects.

He is now 100% better with no issues. And we have a new vet.

Good for Pooper for proving them wrong! Glad he's better!

Tough little guy! I'm so glad he's feeling better.

I am glad to hear he is doing better!

I am so disheartened to know that this injury occurred though. Before reading this, I didn't plan on getting any more shots for my cats, and this situation makes me wonder if sometimes the dangers outweigh the benefits