Have you had the bike up on a axle stand and checked it out?...check the axle nut etc...long shot BUT wont hurt none..

What psi is in it?..maybe deflate it and reinflate to a higher psi (as tyre shops do for a short time)to see if that helps

Was it bought privately?..any chance of asking the vendor?..

All else fails take the wheel out and go have the tyre reseated...