The time to worry is when you get addressed by your pprune name!
Kolibear -
Exactly that happened to me, just after taking off from Norwich a couple of years back. As tower handed me over to approach, I was given a friendly... "regards to Big Al" just before changing frequency.
Never did find out if it was NikNak, but Norwich were great when I was there. I even forgot to book out in person (assuming I could do it over the radio - Oops, force of habit) but they didn't bat an eyelid.