I have used puppeth to generate genesis file in which I set sealing time to 30 seconds. I have set up one miner. Now, I want to change the sealing time to 5 seconds. How can I do that on same blockchain? I am using geth as my node.
Can't provide guaranteed answer, but here are some ideas for you to try:
Check this answer Change private genesis state
In short it requires changing the genesis file and reinit the blockchain, because the period is a constant, but ...
clique -> period is inside the config section, so changing it may be one of the exceptions mentioned
Another suggestion is to try with modifying the config file generated with 'geth --options dumpconfig' if it contains the Clique parameters