HSA issue; overlap with employer plan

Hello! My employer healthcare coverage was slated to end at the end of Feb (this was confirmed via email by the employer).

 

At that point I opened a HDHP plan and contributed $300 to a HSA. Then due to changing federal laws I was able to switch to a better low cost plan that wasnt a HDHP and stopped contributing to the HSA.

 

Now looking at my old insurance site, it says my plan was actually termed the following month (end of March) so it looks like I had my employer plan at the same time as the HDHP plan.

 

What is the best course of action (I have accrued around $40 dollars on the HSA account)?

 

Thank you!