Weakness and stiffness in my hand and fingers

Been dealing with this crap for about a week now, but I wanted to pick your brains here before I go seeing a doctor.

Basically, whenever I squeeze my right hand hard—like when I’m shaking hands or just gripping something tight—trying to open it back up is a total nightmare. It feels completely locked up, like I've got zero strength left to pull my fingers open. All I feel is this intense tension right where the veins and the median nerve are.
I can eventually force it open, but it’s a massive struggle and it keeps happening all day long. It’s super freaking annoying.

Anyone have any clue what the hell this could be? 🤷