If you took a small section off, like 6 inches or so, repairing it may not be too hard. The major question is, was the break "clean". If a crack is running down the rod, than you may not have a shot. But if the tip sheared off nicely or can be cut cleanly, you can put a new tip top on the rod.
Any fly shop should have a few sizes of tip tops. You can bring in the top section, and fit one to the end. It can be glued in place with 30 minute epoxy. Adding a few thread wraps to dress up the rod is nice but totally unneccessary.
Some folks intentionally trim rods down to make a rod action quicker. You may also find that it will cast a slightly different line. For instance it may throw a 6wt DT better than a WF5 now. The more that was trimmed off the end, the more the action will change. Small changes will not be a big deal. Whacking a foot off the end may make for such a stiff action that you could not get a bend in the rod no matter how hard you cast it.
