This little poem comes from Disticha de Educatione of Urbano Appendini, published in 1834; you can see the whole book at Google Books.
Noxius Sibi
Si cuiquam imprudens dictis factisve nocebis,
Noxius in primis tunc eris ipse tibi.
The vocabulary is keyed to the DCC Latin Vocabulary list. There is only one word in this poem that is not on the DCC list:
imprūdens (imprūdentis): foolish, reckless
noxius, -a, -um: harmful, criminal
dīcō dīcere dīxī dictum: say; causam dicere, plead a case; diem dicere, appoint a day
faciō facere fēcī factum: do, make
in: in, on (+ abl.); into, onto (+ acc)
ipse ipsa ipsum: him- her- itself
noceō nocēre nocuī: harm
prīmus -a -um: first; adv. prīmum: at first, firstly
quis- quicquam/quidquam: any (single) person, anyone at all
sī: if
sui, sibi, sē: him- her- itself
sum, esse, fuī: be, exist
tū tuī tibi tē: you (sing.)
tum or tunc: then
ve (enclitic): or
