Hi,

According to the educational eligibility criteria for cms exam notified by upsc in 2019 -

" A candidate who has yet to complete the compulsory rotating internship is educationally eligible for admission to the examination but on selection he/she will be appointed only after he/she has completed the compulsory rotating internship."

So you can appear for cms exam but if you get selected you have to complete the 1 year internship.

Hope it helps.