I have a 3.7V lipo battery with 8000 mah nominal capacity. From what Ive seen online, the charging current should be 8A for a 8000 mah battery. Is that true? Will charging it at a lower current damage the battery?
You should charge batteries always in accord with manufacturer's specifications. Usually they rate the battery for "normal charge" (~0.2 C), and for "fast charge" (at 0.5 or 1.C rate). Charging Li-Po batteries at lower current won't damage anything, it will only increase its current capacity for a bit relative to it's nominal capacity. Always refer to real specifications, not what you read on Internet.
BTW, there are Lithium-based batteries that are designed to be charged at 3C or even 5C rate, which is usually displayed on its label.
If the manufacturers datasheet says 8000mA charging current, it shall be 8000mAh charging current.
Charging with a lower current does not damage the battery but it will extend the charging time.
The only things you should be careful is overcurrent and overvoltage, these may seriously damage the battery. But if you stay within the manufacturers limits, you're fine.