Pain arises in the body as a signal that something is not right, something requires attention. When everything inside is in a natural balance, called homeostasis, nothing bothers us, and we feel great. But when this balance is distorted, the organism will strive to heal itself (for example through inflammation, which in itself may manifest in pain) or to bring your attention to the affected area, for your information and action.
When you take painkillers, your pain receptors got numbed, and you do not feel the pain associated with the problem in the body. But by blocking the pain, you only disrupt communication from your body that something is not right. The longer you ignore or avoid facing pain, the more the problem causing it progresses. You may find yourself soon with a chronic condition, which requires heavy medication or even hospitalization, which could be prevented if you caught the problem causing it earlier, by listening to your body signals.