I'm dealing with something similar now, and it's driving me crazy. I was gradually increasing my exercise to the point where I could walk slightly over a mile a day. At the park yesterday, I took the wrong trail and ended up walking a distance 4x more than what I usually do. In 93-degree weather.

My son drank all of my water on the walk, so I ended up dizzy, nauseous, and exhausted. I almost vomited when I reached my car. I had sun poisoning before, many years ago, so I think some (but not all) of my symptoms were caused more by dehydration/heat than PCS.

My head isn't throbbing anymore, but I did hear the pulse for like an hour. It was like I could hear my heart beating through my brain.

I also have pressure/tightness in the back of my head now. It started shortly after my walk.

I have overdone things in the past, and the good news is that you will probably get back to normal again soon. Sometimes it takes me a day or two, but there have been times where I set myself back 2-3 weeks.