Yep, likely a tiny burr around a spoke hole that is pushing through the rim tape, and causing your issue. Strip the original tape, run over the inside of the rim with a maroon Scotchbrite pad, or some 220 wet-or-dry sandpaper. Pay particular attention to the spoke holes. Clean/degrease with some alcohol on a rag, and apply new Velox (thick cotton) rim tape. That stuff has been made for eons, and simply works.