I was stretching my core and I over stretched.

Is there a specific method for healing this? Is RICE standard or should I apply heat?

RICE if it is sore and inflamed (red, painful to touch, recent injury), heat only in advanced stages if it is not healing.
recent research says ice isnt that helpful anyways and is BS, and you can't really elevate your core, nor can you compress it.
I suggest you avoid painful positions and do some diaphragmatic breathing to calm your ass down

Include stretching in your daily routine. Gentle stretching can improve your circulation and a steady blood flow helps reduce muscle tension and soreness. Make stretching part of your other warm-up and cool-down activities. It will help put you in the right frame of mind before exercise and help you relax afterwards(Indian workouts).