Critical Injuries: Please help, because this is an annoyance I'm facing when I'm running the game

I run Star Wars every wednesday for my group(currently on discord because of reasons, but usually from my home). However, I'm really getting stumped by a rules lawyer who is a non combatant, Force User(with heal/harm) and acts as a medic for the group and attempts to heal critical injuries in the middle of a combat before they can do their effects.

I had a major conflict happen with the group against a Jedi Knight and two underlings, one of them got nearly taken out(four short of the threshold)and got a critical injury "Agonizing Wound", which makes all Agility and Brawn checks have a higher difficulty(because this player is a major combat player, this felt right and fit for the current battle). However, the medic quickly decided to heal him using his heal/harm ability(which he has the range modifier for and did the critical injury heal on his next roll.

Now, I've said that a critical injury should take some time to heal(the initial effects that go for one round or whatever can go away, but I expected that a few critical injuries could build up in a combat and give a higher likelihood of higher damage, lost limbs or death).

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However, I haven't seen anything in the books that say how long you should wait before critical injuries can be healed. Is there any suggestion on that? Something so this person can't just heal a teammate as soon as they take an injury, as power gamers are one of my least favourite things and providing a challenge is what I like(and I don't want to have to drop a dozen sith lords in to threaten them, lol.)