A bluish lump sounds like a ganglion cyst actually. Common.
You don't have to remember how you get bruises, it's VERY rare that I recall how I get one. Most of mine are from bumping things (I used to get a lot on my shins when I worked in an office and had the garbage pail under my desk - obviously I wasn't SLAMMING my shins into the pail, but the mere act of bumping it would bruise them (I guess because there's no fat there, just skin on bone basically) And the other bruises are pressure related. I bruise a LOT more if you press on my skin rather than if you would HIT it hard - you could be the same.
How long have you had this "petechiae"? I put it in quotes because I thought I had that! It started on my leg, then my other leg, then my torso, then my arms.... I looked like I had measles on my legs!! After some of them started to RAISE I realized it was some sort of allergic reaction (I found out it was Flaxseed oil I was taking - that's the only thing new I was doing, I stopped and the entire rash cleared up) - so keep an eye on the petechiae and start feeling some of them and see if any are starting to raise (petechiae won't raise) Also it could still be a rash even if it doesn't raise. Think of any new foods, medications, supplements or laundry detergent you started to use when you noticed this.