Thhe boy hasn't eaten for three days ; they are poor people and there isn't much food in the house. But it barely resonates with his stomach anywhere; he's used to it ( and doesn't know any beter, i.e, doesn't know the feelong of having a full stomach.)

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Note added at 1 hr (2022-12-08 00:18:46 GMT)
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"betTer", typo, sorry;

I think the sense used in this text of the verb "resentir" is a non-pronominal Latin American one: "También se usa como transitivo, especialmente en América, con el sentido de ‘sufrir las consecuencias negativas [de algo] o sufrir [por algo]."

Suffer from: "Do you suffer from any allergies?"

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Note added at 1 hr (2022-12-08 00:19:17 GMT)
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As a possible addition: "He barely suffers from any hunger pangs." This includes the sense of stomach, without mentioning it directly.

Spanish term (edited): resentir -> apenas lo resiente

..... en alguna parte de su abdomen : in any part of his abdomen (coll. gut).

Hint: start from pre-existing ProZ glossary entries and extrapolate. ProZ SPA/GER: in Mitleidenschaft ziehen = take the hit.

Otherwise, dictionary entries resentirse include suffer from or feel the effects of.

el muchacho: the boy or (BrE) lad vs. whippersnapper.

"Register" in either the transitive sense of "to perceive", or the intransitive sense of "to make or convey an impression"
https://www.merriam-webster.com/dictionary/register

I think you could word it as "he barely registers it somewhere in his stomach" or "it scarcely registers somewhere...".