Below is the text as given in the First Folio:
The prayfull Princesse pearst and prickt
a prettie pleasing Pricket,
Some say a Sore, but not a sore,
till now made sore with shooting.
The Dogges did yell, put ell to Sore,
then Sorell iumps from thicket:
Or Pricket-sore, or else Sorell,
the people fall a hooting.
If Sore be sore, then ell to Sore,
makes fiftie sores O sorell:
Of one sore I an hundred make
by adding but one more L.
Pricket, as already mentioned in the question, means "male deer in its second year, whose antlers have not yet branched" (Wiktionary).
Some say a Sore, but not a sore,
till now made sore with shooting.
These lines contain a play on two meanings of "sore": (1) a buck in its fourth year (which may be an allusion to "haud credo" at the beginning of the scene) and (2) the buck being made "sore" (having pain) by the princess's arrow.
The Dogges did yell, put ell to Sore,
then Sorell iumps from thicket:
"L" (or "ell" in the Folio) was "pronounc[ed] with a prosthetic 'y' by the Elizabethans, so that it sounded like 'yell'" (Kerrigan, page 191). Hence, "ell" is involved in two word plays: (1) with the dogs' "yell" (i.e. bay) and (2) adding "ell" to "sore" gives "sorell", i.e. a buck in its third year (see Hibbard, page 155).
Or Pricket-sore, or else Sorell,
the people fall a hooting.
"Regardless whether it was a sore/wounded sore or a sorel(l), the people started shouting. (Kerrigan mentions that they might have shouted, "Sola, sola", without explaining why that is relevant here.) Kerrigan thinks that "Pricket-sore" and "Sorell" may be bawdy without explaining how. Eric Partridge's Shakespeare's Bawdy has no entries for "sore", "sorel" or "pricket"; it has an entry for prick, which does not require an explanation.
If Sore be sore, then ell to Sore,
makes fiftie sores O sorell:
If it is a sore (a buck in its fourth year) that is sore (wounded), then adding L (Roman numeral 50)/ell to sore, makes (both) fifty sores and sorell.
Of one sore I an hundred make
by adding but one more L.
Adding one more L (50) to L gives a hundred; but "more L" may also be a play on "moral" (i.e. the story's moral).
Sources (other than Wiktionary):
- Love's Labour's Lost. Edited by G. R. Hibbard. The Oxford Shakespeare. Oxford University Press, 1990.
- Love's Labour's Lost. Edited by John Kerrigan. The New Penguin Shakespeare. [1982] Reprinted with revised Further Reading. London: Penguin, 1996.
- Partridge, Eric: Shakespeare's Bawdy. London: Routledge & Kegan Paul, 1968.