I donated blood today, and as always it was a bit of an adventure. They used the opposite arm as normal, which surprised me but I don't really care which they use. Getting the blood to flow into the tube was a little hard, but once it was going is was going well. But then I got a hematoma - apparently some blood was leaking a bit into the surrounding tissue, causing a small bump and the flow to slow way down. We moved my arm around a bit and it started flowing enough to finish up. (Phew.)
I had to ice it for a bit right afterwards and then I applied heat this evening. There's still a bump, bit it might be getting a little smaller. My elbow is also slightly sore, but just barely. They kept talking about the bruise that might show up - I usually get a pretty nice bruise a few days after donations, so I'm kind of hoping this one is awesome.