This is a Lamp

Few weeks ago I had to change my rear right tire as a nail poked through it (horrible urgh, thank god it was parked at the house then). Luckily my spare tire was a good substitute, and had it aired up after replacing it. All is good, nothing is wrong with it until...

2 days ago, driving down casually then the dashboard turned red stating "Check tire pressure". This got me worried, and scurried back home and checked the tires straight away, but found nothing at all. Nothing seems to be amiss, but took a precaution anyway and drove another car yesterday to work to see if a flat tire might come by. Got home from work, but still the tires were fine .

I started the car, and it says "Reset tire pressures after changing?"
Well, I did reset it from the menu and drove around a couple of short distances but nothing still. Am I having an illusion ? lol

Does it mean that I am resetting the sensors since I put new tires in?
Why did it sense the new tire late though (after a few weeks of use)?

C300Sport

From what you wrote, it sounds like you don't have a tire pressure gauge. If you don't, you need to buy a quality gauge and check your tires on a regular basis as the system on the car is only going to warn you once the situation is pretty bad.
The best way to reset your tire pressure is to let you car sit, preferably overnight, and then check and adjust your pressures to what is on your tire pressure placard/sticker.
Once everything is correct, then save your settings. If you just randomly save your setting when your tires "look good" you could have them at 5 or 10 or more PSI off without even knowing it.

This is a Lamp

No, I do not have a tire pressure gauge as you said. But I did leave it for a day to settle down (the day I took another car to work). I will head over to the pump station to check later, thanks for the reply