Hmmm, it looks pretty full and they do tend to detach themselves once they’ve fed. When was the last time you inspected your leg as it may have been there for a few days? Speaking as someone who’s had Lyme disease you really want to keep an eye on it. When I found a tick on my leg after Bristol Bikefest 2 years ago it was on the Tuesday after and I’d had 2 showers before I even noticed it.
You can have a blood test but they aren’t that reliable until the antibody has formed as it’s that they test for. The sooner you catch it the more effective the antibiotics are so personally I would visit your doctor for advise. I had to go twice before they would test me. The first time he said it can’t be Lyme disease as there was no bull’s eye rash, which I found later to be not true. Two or three weeks later I started to feel like crap (a bit like having the flu) which lasted longer than it should have. The doctor then agreed to test me and it came back positive.
The first 3 week course of antibiotics eased the symptoms for a few weeks but I then needed a much stronger 3 week course as the symptoms returned.