Learn Finnish: En hotki, koska muuten minulle tulee hirveä ähky! - I do not wolf down, because otherwise I will get a terrible food coma!

In Finnish, physical states, feelings, and ailments (like hunger, a cold, or a food coma) usually 'come to' you. You use the allative case (-lle) with the verb tulla. You generally use saada (to get or receive) for acquiring physical objects, like a gift or a letter.

What exactly does ähky mean?

Ähky is a very common everyday word for the uncomfortable, bloated feeling you get when you have eaten way too much (often translated as a 'food coma'). Fun fact: in veterinary medicine, ähky also refers to colic in horses!

Does the verb hotkia undergo consonant gradation?

No, the consonant combination tk does not soften in this word. It is a Type 1 verb that keeps the tk throughout all its forms: minä hotkin, hän hotkii, and the negative form seen here, en hotki.

The English translation uses the future tense ('I will get'), but tulee is in the present tense. Is there a way to make it explicitly future?

Finnish does not have a separate grammatical future tense, so the present tense is used for both present and future events. The cause-and-effect context of koska muuten (because otherwise) naturally implies the future here. While you could theoretically use a compound structure like tulee olemaan, native speakers almost never do this for everyday statements.