It is really hard to tell you what happened to your PC. Trying to hold the power button was a good idea, but you need to have both the power cable and battery disconnected when doing it. Are you sure your laptop does not have a battery or it is just not possible to remove it. There are some models which do not allow the battery to be easily removed. Please check the laptop’s manual if there is some button configuration you could use. I would seek assistance from a technician, because you may need to have the power port and the motherboard checked.