Our company should designate an outdoor smoking area because the smoke gets in my eyes in this room and it hurts.
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of pain? It's painful. It's also when you say ow and ouch.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: An eater (いた) is someone who eats. But, the eater hurt his mouth. So now it's painful to eat.