high bpm still 1hr after workout

22F I did a little 15mins cardio workout an hour back and i normally don’t workout a lot so my stamina is low. during the workout my chest was pounding but then i settled and had my dinner Now i checked my heartbeat as im feeling some anxiety and it’s like 120bpm like my pulse is beating fast even thought im just lying down in bed is it just anxiety? every time i get my bpm checked or bp i do tend to get anxious but now it just feels different as i just worked out. I had a treadmill test and a 2d echo a month back and they came normal (as part of a health checkup)