Do I need to liquid cool my PC?

You don't *need* to liquid cool. Until you get to the high-end of liquid coolers, air coolers are generally preferable (plus they have fewer problems).

You have a competent budget cooler there. That should be ample for you to at least see how your 7700k functions and decide on a cooling solution from there.

Do you already *have* the 7700k? Because if you're in an area with good availability of tech products and don't already own the CPU and the motherboard, a Coffee Lake 8600k is just as good a recommendation and the 8700k may not be much more expensive (and is a 6c/12t CPU rather than 4c/8t).

If you go AIO, make sure it's something with at least a 240mm radiator. For the 120mm ones, I'd rather have an air cooler at the same price.

Short answer... No, you do not need liquid cooling.

If you are overclocking, perhaps you might want a stronger air cooler.

Since you already have the cooler, go ahead and use it.
What is your case?
How effective the cooler will be will depend on your case and intake fan arrangement.

What is your cpu temperature at idle and under load?
I would expect the idle temperature to be around 10-15c. over ambient.
Under load 75c. would not be bothersome.
The processor monitors temperature and will slow down or shut off if it detects a dangerous temperature.
That will be around 100c.
You can monitor your temperatures with HWmonitor.

If you have 160mm available for a cooler in your case, there are a number of good air cooler options.
All are likely to be better options than a aio liquid cooler.

My canned rant on liquid cooling:
------------------------start of rant-------------------
You buy a liquid cooler to be able to extract an extra multiplier or two out of your OC.
How much do you really need?
I do not much like all in one liquid coolers when a good air cooler like a Noctua or phanteks can do the job just as well.
A liquid cooler will be expensive, noisy, less reliable, and will not cool any better
in a well ventilated case.
Liquid cooling is really air cooling, it just puts the heat exchange in a different place.
The orientation of the radiator will cause a problem.
If you orient it to take in cool air from the outside, you will cool the cpu better, but the hot air then circulates inside the case heating up the graphics card and motherboard.
If you orient it to exhaust(which I think is better) , then your cpu cooling will be less effective because it uses pre heated case air.
Past that, A AIO radiator complicates creating a positive pressure filtered cooling setup which can keep your parts clean.
And... I have read too many tales of woe when a liquid cooler leaks.
Google for AIO leaks to see what can happen.
While unlikely, leaks do happen.

I would support an AIO cooler primarily in a space restricted case.
If one puts looks over function, that is a personal thing; not for me though.
-----------------------end of rant--------------------------

Your pc will be quieter, more reliable, and will be cooled equally well with a decent air cooler.

Was this a custom loop or an AIO? If the latter, not much you can do there.

Unless you're spending $80 on an AIO or more, you're likely better off with a Cryorig H7 or a number of Noctua air coolers.

If you have the budget, then you could go full custom again. Won't help you with an AIO.