As has been said, it's perfectly normal for PSA to rise for RT-treated prostate people when the hormones finish, and '2' is the upper range of that. If it continues to rise, then will be the time to be concerned.
It's called a "PSA bounce"is usually a reaction of the remaining normal prostate cells after being released from the hormone suppression. It will usually drop again, but not to the almost zero experienced during the hormone therapy.
It is conceivable - but unlikely - that it is more serious than that, so if there's no other issues, there's probably no need to worry too much.
A referral back is the safe and sensible thing for a GP to do, but a repeat PSA, if you have to wait for an appointment, would be a useful action, too.