Can I Move?

Absolutely. Keeping still is not necessarily a feature of meditation. What matters most is being mindful as you move. For example, you can first notice the impulse to move before following it quite consciously.

There are also meditation techniques that take place in motion, such as walking meditation or mindfulness during yoga. With some techniques, such as a body scan, it does make more sense to move as little as possible because this allows you to notice subtler physical sensations. But of course, the same principle applies here: you do not have to stoically tolerate pain or parts of your body falling asleep.