Should I tell my current boss a new job opportunity became available for me?
Do you think you should tell your boss about it?
I must be honest about the situation.
It's good of you to be honest about your future opportunities with your current boss. Your boss will appreciate it and there may even be a place for you in your original company if things go bad in your new place.
I think I will continue my work at my current boss, why should I switch firms?
Staying with your current job is a fine decision if that's what you want to do. Switching jobs can be very stressful, but if you do end up doing it be sure to tell your boss in advance so you don't burn any bridges.