The noun headache has 2 senses (first 2 from tagged texts)
1. (5) concern, worry, headache, vexation -- (something or someone that causes anxiety; a source of unhappiness; "New York traffic is a constant concern"; "it's a major worry")
2. (3) headache, head ache, cephalalgia -- (pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs)