Now my questis, where can I find previous mined block headers and solution nonce? Something that I check validity by myself.
Depends on how you mean to
check it yourself. There are two interpretations.
- The easy way: run bitcoin-cli getblockheader <BLOCK_HASH>, and check yourself the block header (with nonce included). You can also run bitcoin-cli getblock <BLOCK_HASH> 0 to get the raw block data (the zero indicates that it will return hexadecimal string).
- And the hard way: write the functions that perform block header validation from scratch.
I think you mean the former.