"I am Raj."
Translation:मैं राज हूँ।
It produces a nasalized n sound. It's called a chandrabindu(moon dot). I suggest you to listen to its pronoucnciation on google translate if it was for some reason not working here.
No significance. Unlike the anuswar ं which sometimes indicates a plural (है vs हैं), ँ is just a pronunciation element like any other sound in the language.