Doubt the truss rod needs a tweek, not if it's just one fret on one string.
First thing I would be checking is the height of the adjascent fret. Has it lifted slightly?
Get yourself a straight edge and place it across three frets, (the offending one and the neighbours on either side) see if it rocks. If it does, then you have a high fret.
A credit card makes a decent enough straight edge