This phrase has been diagrammed for your edification.
A few notes:
The main (last) word of this sentence is Have-End-V-2. Have's patient is a verb. To "Have a verb" in rikchik means that to be able to do something or to bring something about. (It should not be confused with the past tense, which uses Sequence.)
The patient of Have is Sequence-Patient-V-2. This is a sequence of events, but not necessarily things that have actually happened. In this case, it's two potential events that the speaker asserts it has the ability to cause to occur in sequence.
The first event is Me-Agent-R-0P Glass-Patient-T-0 Mouth-Patient-V-2. There is a pronomial on Me, indicating this is the same Me that is the Agent of Have. (Don't ask what it would mean to be a different Me.) The phrase simply describes the eating of glass. (Mouth means Eat when in a verb form.)
The second event is Me-Example-R-0P Zero-Quality-M-0 Pain-Patient-M-2. Example is the reciprocal relation of Quality. This phrase could therefore have been written Zero-Quality-M-0 Pain-Quality-M-1 Me-Patient-R-1P, but that would emphasize Me ("Painless Me") instead of Pain. This phrase might be translated "No pain (to me)". (I could have used the glyph "Happy" but the original sentence did not say "I enjoy it", merely "it does not hurt me".)
These two events are brought together by the Sequence. This does not explicitly assert causality, but it's strongly implied. (Imagine a comic strip of someone eating glass in one panel, and smiling in the next. That's the level of implication we're seeing.)
The retranslation of this would therefore be something to the effect of, "I can make this happen: I eat some glass, then I'm not in pain."
A final note: don't expect rikchiks to be impressed by this unless they are very familiar with human physiology. Rikchiks can eat pretty much anything, including glass, without discomfort.