My daughter (a dancer) had acl surgery two years ago. She took a dance class yesterday and her knee hurts today to move it and is slightly swollen. She has been using ice, rest elevation and anti inflamatory meds should we take her to get an MRI or wait a couple of days. She had not danced since May although she has been physically active in other ways

You should consult with the surgeon who performed the ACL repair.

Being physically active doesn't mean that the muscles/tendons/ligaments that are used for dance are being exercised.

Do what J_9 said because she's REALLY smart.