I setup my ledger nano s properly and transferred my Ripple to ledger nano. Now I want to reset my ledger nano and generate new seed. I have transferred Ripple to some other exchange to reset my ledger but last 20 ripple can't be transferred as it is required for any ripple account. Once I will reset my device, can I use the same ripple wallet so that my 20 ripples won't be lost or I will have to forget these 20 ripples in terms of resetting my ledger nano? Is there any other way to save these 20 ripples?
Since your Ledger's Ripple address is tied to the seed, if you reset the device and choose a new seed, you will lose those 20 XRP.
If you reset the device and restore the old seed, you can reuse the address.
There is no way to use a new seed and the old Ripple address on a single ledger.