My toddler bites himself in frustration

My toddler has a habit of biting either himself or others if he’s really frustrated or overwhelmed. It’s usually himself he bites. He bites hard to. Leaving a mark. Not enough to bleed or bruise though. He will bite his arm if he is really angry, frustrated, or even being overly tickled sometimes. (We make sure he’s ok with being tickled. Once I see biting I immediately stop)

Do you mamas have experience with this? Tips on how to find a better way to calm himself down without biting? I’m trying the gentle parenting method. Right now I just sit with him as he’s getting frustrated to show I’m listening.

He’s 2