Can you get such an erection that your penis blows up?

not simply by getting an erection. An erection is caused when the capillaries carrying the blood round the penis constrict causing higher pressure, but they will never constrict so much that they burst or 'blow up', as you put it.

It is possible for damage to be caused similar to this if the erect penis is bent too far though; 'fracturing' the penis causes an audible snapping sound, unbelievable pain like no other and an incredible amount of damage to the inside workings which often have permanent effects.