does anyone knows how can i solve

Error: Validation Failed: 1: this action would add [2] shards, but this cluster currently has [3000]/[3000] maximum normal shards open

i know elasticsearch suggest some default solutions like re-index indices or delete prevues indices but i have two problem one i cant remove indices because elastic now is live on productions and data are important, second indices are more than million some of them are two huge i cant calculate how much time does it take to reindex completed and elastic be available for end users of course i cant add more data nodes because elastic clustering deployed with docker on three seperate servers so if i want to add more nodes i have to restart entire container so it’s impossible.I looking for some kind of solutions that solve my problem with lowest cost. I have to add this elastic deployed on ecommerce website with more that millions indexes, and this not my job just I have to maintains to increase performance of elastics