Let them ripen, cut off the damage and eat them. it'
s not a disease, it's physical damage.

Double check your watering practices - it's usually the result of insufficient water while the fruit is rapidly growing.

or i heard if you overwater it can also cause this.

It's erratic water supply such that the calcium doesn't get to where it should go.

Agree with Jean - it is inconsistent soil moisture levels - dry, then wet, then dry, etc. - a common problem with plants in containers unless you use a timed drip system of some kind. That and/or too much nitrogen fertilizer.

Personally I pitch them as I think it removes some bit of stress from the plant and that the BER affects the taste but not all agree with that so try some and see what your taste buds think.

Dave

Remove it then eat it. Then fix your soil

Here is a link that might be useful: tomato diseases