If you are/start having concussion symptoms (confusion, dizziness, disorientation, forgetfulness, nausea/vomiting, etc.) you should get checked out at an ER or urgent care. The symptoms aren't always immediate. They'll probably tell you to wait it out, but getting evaluated is better safe. I'm surprised you don't have such an awful headache that the idea of working out is repugnant.

If you have enough muscle tightness that it's causing numbness down your arm, you're compressing a nerve plexus. Numbness like that can lead to weakness too, which is dangerous when you've got the bar over your head. Focus on relaxing and stretching out your neck for now, and apply some heat/massage. Take rest days until full feeling returns to your arm, and you can use it as well as before. Avoid yoga poses that require full arm support (such as downward dog).

Working out very tight muscles isn't always the best option, and with a head injury, you want to be careful. Weight lifting increases abdominal pressure, which in turn increases blood pressure and intracranial pressure, and if you have something bad up there, IICP is a bad thing - even a minor spike. If you absolutely must work out, stick to body weight until your arm is back to normal.

But, IMO, a few days off isn't going to wreck your progress, and you don't want to injure yourself further. (I'm a nurse.)