Hello, My Son Was Hit In The Temple Area On

Hello, my son was hit in the temple area on the side of the head with a large buffalo dog bone while fighting with his brother. His brother threw the bone at him from about 6 feet away. My son is 14 years old. This happened 4 days ago. Today he began complaining of a terrible head ache, blurred vision and was very irritable. I treated him with Motrin and he is resting. I am wondering if it is possible to get a concussion from such an event and if it is possible to have symptoms 4 days later. His headache hurts worse on the left side, which is where he was hit.