Ok, this morning, I was walking inside and as I closed the door while facing it, it hit the side of my kneecap. Now, it hurt pretty bad at first, but I could still walk. The pain lessened, but now its worsening. There is a slight bruise, but there is no swelling or signs of displacement. Could I have injured it or is it just a little bruise, or is it worth going to the doc for?
Wrap some ice on it for 15-20 minutes on, then same time off. Do a couple cycles, take an anti-inflammatory (aspirin, advil…). If you have tenderness to the touch in the morning, or it gets worse as you walk on it throughout the day, see a doctor. There’s some soft tissue there that can bruise, but it’s more likely to injure that kind of stuff by spraining or tearing, not by impact. What you want to watch for is if that gets inflamed and begins to get aggravated by the bones that move around there. Couple years ago, I had surgery to release (literally cut loose - i forget the fancy doctor word) my kneecap because of old inflammation/scar tissue that had caused my kneecap to pinch/irritate the soft tissue on the outside of my knee.
Wow, what a long answer from a non-doctor huh? But I DO know knee injuries, and that’s what I’d do if I was you. Err on the side of caution.
From the little and vague info available, it sounds unlikely (but not impossible) that you’ve injured your knee in a serious way.
I agree that you should treat the symptoms and see what happens. If you’ve done serious damage, it won’t get better in a short amount of time (2-3 days). If you’ve gotten a nasty knock, odds’re (though not for certain) that it’ll be noticeably better in 2-3 days.
This is all assuming that you’re able to function normally - you know walk, sit down, stand up etc.