The same thing happened to me the last time there was a market correction, in 2018. I bought a Vanguard fund for the very first time only weeks before the whole market dropped by over 10%. It was a really frustrating first investment experience, but I read here and elsewhere that I should just stick it out and add money as normal, so that's what I did.
By January 2020, my portfolio had gained over 14%, despite the painful start. That's an excellent return for 1 year and 3 months.
So, just stick with it for now. If you can, add more money to your investments but most importantly, don't sell anything! In the long term, it will go back up.