Looks like one, though I am not sure. Is it possible to take a picture of the tail tip under light so we can see better? Is the tip dry-ish and feels rotten? If it is might have to take it to a vet to make sure it's not spreading.
Causes of tail rot are:
1. Injuries/trauma - caused by falls, or by any other bearded dragon.
2. Malnourished - make sure he has a balanced diet and he gets the nourishment he needs
How to identify tail rot:
1. Dried out - Decaying tail won't be able to retain moisture, check if it's dried out completely.
2. Very thin, brittle - Decaying tail won't be able to process nourishment, causing it to become more thin and brittle.
What to do after finding out it has a tail rot:
1. Go to a vet - very recommended
How long has the end of the tail looked that way? I'd keep a close eye on it and if the shriveled area appears to be moving up the tail, it should be addressed by a vet. If it stays the same then it may be fine on it's own. Likely caused by a nip from a tankmate at a young age which is unfortunately, common.