Sore Forearm (Rhythm Piano)

My forearm has been sore—inner arm, just below elbow—while playing. Is this normal for new players, or is something obviously incorrect with my form? I’ve also attached a video.

I’ve just started playing piano, learning through the PianoforAll program. I’ve been playing nearly every day for two weeks, anywhere from 15m to an hour, including time watching videos and reading pdf material.