yea, Tushar and chaharrachana is right, meaning of expert in Hindi is " विशेषज्ञ( Visheshagya) and Mahir(माहिर) " " विशेषज्ञ( Visheshagya)" is well known word for specialist and expert among hindi speakers.

प्रवीण = pravin, तरबेज = tarbej, कुशल = kushal, निपुण = nipun, पारंगत = paarangat, माहिर = mahir और (aur)_ विशेशग्न्य = wesheshgny Although all the above are interchangable, we use / write it in different context, explaining the speciality. Some of them are used in mythological forms as they are derived from Sanskrit language. In commercial writing one may not replace them.

pratishthit or mahir or visheshagya

visheshagya विशेषज्ञ