Your camera has not been hacked. There is no known way to hack an iPhone, much less the camera. As such there is no way to know one way or another. Even the current hacking software in the news is said to leave no trace, so no way to know if it was used or not.

You can determine if your iPhone camera has been compromised by monitoring several key security indicators, most notably the green dots in the Status Bar. Apple's iOS includes a hardware-linked privacy feature that displays a green light in the top right corner whenever the camera is active; if this light appears when you are not using a camera-enabled app, it is a major red flag. Other signs of a hack include an unexplained drain on your battery or the device feeling unusually warm, which suggests malicious processes are running in the background. You should also check your "Mobile Data" settings to see if an unknown app is using a significant amount of data, as hackers need to transmit captured footage to their servers. Additionally, reviewing your "Privacy & Security" settings to see which apps have "Camera" permission can reveal if a seemingly harmless app is overstepping its bounds. If you notice "ghost" photos or videos in your library that you didn't take, or if your phone frequently glitches and restarts, your device may have been breached by spyware.