Would 'worsening symptoms' develop nearly 2 weeks later?
 

Sorry for the second thread on the issue. I was fairly content just to rest and recover, but today I had a raft of fairly new symptoms. I've had a developing fairly major fever for most of the day and in addition to that had pretty extreme nausea that felt like I was going to vomit when I ate.

Would concussion symptoms develop this period later or after a couple of weeks is that likely to be just an unrelated virus?

Concussion symptoms can develop weeks later. But, a fever is NOT a concussion symptom. Fever can make concussion symptoms worse.

But, I don't think your nausea is related to your concussion. It is more likely related to whatever is causing your fever.

Yes, most definitely symptoms can be delayed.