RubberWatch writes:

I am a student pilot. I was out flying solo today and was instructed
by ATC to fly a heading of 210. I thought he said 110 and I flew on
that heading.

Did you read back the heading? If you read back 110 and he said nothing,
you're okay, since he should have corrected you. If you read back 210 and
then flew 110, that's potentially a problem (although probably not in this
case, since you fixed it). If you didn't read back the heading, that also can
potentially be a problem because the burden is upon you to fly the correct
heading if you didn't read it back.