I believe I have swept the private keys somehow. Wasn't I supposed to use the original wallet keys of the actual wallet from which I have initiated the sweep?
For sweeping, you need the private key. If you do so, you have surely exported the private keys from the original wallet.
I had the funds in some wallet -> transferred to this new wallet which was created from scratch. Then I have saved the seed somewhere. Then I believe I have use the SWEEP on this wallet and pasted some private keys. I'm not sure which private keys or how did I do it. So what can I do in this situation?
If that's the case, now you need the seed phrase of the new wallet (the one in which you swept your private key) to access the fund.