Hi, I have a grand cherokee zj 1993 4.0L inline 6 and a few days ago it overheated. Turned out to be a stuck thermostat. We changed it and started the engine and it runned well. I need some opinions trying to know if the HG blew since I have no leaks, no oil in the coolant or coolant in the oil, it does not overheat (reaches the normal operating temperature and doesn’t go higher than that) the only thing is that sometimes there’s a little bubble of air in the water reservoir, but maybe it’s normal since the system is still getting water everywhere. What are your thoughts on this?

Sounds like you're good to go to me; you've looked for all the normal signs/issues, and since it runs fine and doesn't have any of the symptoms you have listed, it should be fine.
Enjoy your Jeep!

Sounds like you did the right thing right away and the air bubbles are just working their way out.

Update:
Guess my bad luck got the better of me, turns out after some little use of the car to transport some debris in a trailer we needed to rev the engine a bit to get out of the mud. After that when the engine was hot it was difficult to make it start again. We decided to check the water reservoir and there was just a bit of water left and then we checked the engine oil and what was our surprise when we saw that magical milk oil.
Guess after all the engine wasn’t good.
My father is not happy at all of course since here these cars aren’t really cheap and used so the engine replacement shouldn’t be too cheap. Do you guys know more less the price of replacing or repairing the engine? Thanks