I received the moderna vaccine approx. 2 weeks ago and developed a knot at injection site. it is unsightly, hard to the touch and the size of a small egg. has not responded to icing. how long do these knots typically last?

Delayed inflammation at the injection site, typically starring 10-15 days after the shot, occurs with both the Moderna and Pfizer vaccines. (Not yet known about other vaccines.) It's not an everyday side effect, but it isn't rare either. It isn't dangerous and will clear up in a few days. In the meantime, it's OK to take meds like ibuprofen or naproxen, which probably will help with the symptoms.