You don't
need a new barrel but if he just whacked it off then you definetly need to have it turned down properly at the proper place on the rib. It should be smooth and the end of the muzzle should be square to the barrel.
When a man at the gun club looked at my gun he said that barrell was modified.
He probably meant that someone had gone and modified the barrel by shortening it. I assure you that if it had screw in chokes the rest of the barrel is just a straight bore. There is not choke to it at all. A 12 gauge bore diameter is .729 inches. You can measure this at the muzzle with a caliper if you have access to one.
You can have the barrel recut for chokes. This is not a cheap thing to do. You would be looking at a minimum of a hundred dollars to do this.
After saying all of this I would get your uncle's butt to buy a new barrel for it regardless. Unless he had permission to shorten it.