My left knee isn't happy

Back on December 18, 1994, I stretch my medial collateral ligament (MCL) on the left knee while skiing. I was back on skis on January 12 of the following year.

For the past few days, I felt that same ligament and today, while skiing fairly hard with my daughter my knee bothered me more than ever before. I don't know if I'll be able to keep skiing or if I should take some rest.

Perhaps wear a brace? I really don't know what to do and fear how it's going to feel tomorrow. Any recommendations?