So today I did my usual ~4 mile commute (I've been riding to work daily for about a month now, other than that am basically a newbie cyclist) and my knees hurt just a bit when I arrived at work. The inside of my knees specifically. I really want to stay healthy and pain free long term, so I'd like to know what I'm doing wrong! It wasn't serious pain and didn't last very long, so I'm not in the damage zone, I just want to make sure that I break any bad habits that I may be starting off with. Any input would be appreciated.

BTW, I don't have clipless pedals or clips (yet) and I'm riding a mtb/hybrid - no suspension, slick tires - if any of that matters.

Thanks for your help!