If you mean it's a 20s battery, and your charger is for 22s battery, and it's for a common 4.2v-fully-chargd cell chemistry, then that means it's mroe than 8 volts above what your battery would be fully charged at.
If your battery has no BMS, it's going to shorten it's life, or damage it, or even potentially start a fire depending on the condition of the battery and it's cells.
For 20s, that means each cell would be overcharged to 4.6v, instead of 4.2v, assuming it's perfectly balanced.
If it's not well-balanced, then the overcharge will be greater on some cells than others, especially if some of them have less capacity than others, and/or higher internal resistance. If it's bad enough, it could start a fire at worst; at best it would damage the cells and potentially make the battery unusable (at least unsafe to use).
If there is a BMS on the battery, and it is set to stop discharge once any cell reaches it's full voltage, then as long as teh BMS works correctly it will protect against the overcharge. But if the BMS fails or does not have that kind of protection, then the previous stuff still applies.
Alternately, you can check with the charger manufacturer to see if it is adjustable.
Or there are quite a few threads about opening up chargers and adjusting them; if you're willing to risk damaging it while experimenting, you can look them up and see if they help you adjust yours.