Some brushes shed for a while and some some don't.
Let it dry out completely and run a fine tooth comb through it starting as low down the knot as possible.
If it's a densely packed knot theres probably quite a few loose hairs still to come out and the comb will hasten that.
A couple of sessions will get rid of the loose hairs.
If the hairs continue to shed, especially when the brush is wet, it may have a problem.
That said, I had a brush that kept shedding for several months, 3-4-5 per shave, then it stopped and it's fine now.
A shaving brush can have around 14000+ hairs packed into the knot so it can afford to loose quite a few.
regards, beejay