Just had my 3rd booster. Had the same lymph node thing for two days. Weird, reminded me of when I had cat scratch fever when I was a kid. Also felt like crap for exactly 24 hrs. Nice fever too, slept like a baby.
On the heart subject, after I had covid the first time, I had some weird high blood pressure randomly. Wife bought a cuff a while back and I randomly decided to check my BP about a month after I had Covid. It was crazy high, and the weird part was that my diastolic was crazy high too, not just systolic. Never had high BP in my life, and no family history of it. Went to the doc, they almost sent me to the ER. Put me on some drugs for it and got it under control. Now I'm back to normal. BP wise anyway.