Accidentally, I have transfered BTC from my one wallet to another twice on the same address. First transaction was successful, but in the second case the BTC got deducted from one of my wallet but not credited into my other wallet.
Help how to get my bitcoins back?
It is not clear what exactly happened.
If you've made two subsequent transactions to the same address that should not be a problem. Addresses can be used more than once to receive money.
If you created two transactions that spend the same transaction outputs, there is no problem, because only one of them can confirm.
If your transaction simply didn't get confirmed yet, there is little to no problem: Transactions either have confirmed or have not. Since both wallets are your own, the money is still in your sending wallet until it is in your receiving wallet. If you wish to get help about fixing a stuck unconfirmed transaction please refer to: Why is my transaction not getting confirmed and what can I do about it?
If your question is not covered by these three scenarios, please edit your post to clarify what you're asking.
