I would like to know the time estimate for a brute force attack to break my input (128-bit) which means
2^128 possibilities are there. Any online tool for that or any article which talks about that?
This highly depends on your hardware. You can check online how many hashes may be calculated per second using your algorithm of choice.
Considering that a proper cryptographic hash function is not reversible and not predictable, brute force is the only method which can be used.
If the algorithm in question outputs 128 Bits, there are 2^128 possible hashes, so it's a huge space to explore. As you can't predict which digits will change as a result, if you flip a single bit of the input, there are not "hints", it's just (kind of) randomness, remember this! Generating 2^128 Hashes is not guaranteed to produce your target hash! It's always a chance but as you can't predict anything, you can't be sure when you will hit your target hash.
tl;dr: Just look up how many hashes per second your hardware can achieve with that algorithm and then consider the possible space to explore (2^128 Hashes in your example). Then calculate the probability per hash execution.
Edit: Misread the question a little bit and crossed out the incorrect part. As the question states, the input is 128 Bits, so there are in fact only 2^128 possibilities, in order to find the correct one. Thanks SmokeDispenser for pointing that out.