After hiking on a rugged mountain trail, my knees ache, and I'm worried.

I mainly used well-maintained flat walking paths for my walking exercise.
I went hiking over the weekend because the autumn foliage was beautiful and the weather was nice.
Climbing up and down the rugged mountain trail, my knees ached that night.
I thought it might be something minor, so I applied Mentholatum lotion.
I think I was feeling a bit better the next day.
But after walking on a flat trail for about an hour the next day, my knee started aching again.
Before hiking, walking for about an hour a day was no problem.

How should I manage my knee when it feels sore?