Smell it. Does it smell like a tomato, or more like tomato leaves/stems?
If it smells like a tomato fruit, it’s already ripening.
I’d pick it, and then let it continue to ripen inside. Eat it before it gets too soft.
Man that may be tough. The whole plant has a wonderful tomato smell. Even my Better Boy with no fruit yet.
They’re kinda hard to get to, as well. Deep inside.
Thanks for the advice. I’ll try picking one in a day or two and see what happens.