the right way to identify LED ratings is to know it's maximum current rating. Chinese models withstand lower current/voltages as opposed to the standard ones. If you have a full supply of 5V output from a 7805 a 670Ω resistor is optimal, but if you just want it to be noticeable you can even use 10K. It's up to you, given the range.
It isn't voltage necessarily that burns LEDs, but over-current. That's why a limiting resistor is used in all LED circuits as a rule.
Generally speaking, most LEDs want less that 20 milliAmps of current, and 10 milliAmps is a good safe number. Use Ohm's Law to figure the resistor based on initial voltage less forward voltage of the LED divided by .010. Hint: it will usually be in the hundreds of ohms.