Hello aspirant

Yes ,It is totally worth for you to pursue Msc physics along with your UPSC CSE preparation as you can choose Physics as your optional in the CSE exam,Physics is very popular and scoring subject for optional point of view also MSc in physics  will act as a backup plan(which is very important keeping in mind the uncertainty of this exam) for you as you will be eligible for so many government and private jobs.

Hope this helps.