I placed 4 Tomcat poison blocks in my apt. Today there are nibble marks. Ugh. Now what?

Yes, if it is infact mice there will be nibble marks on the blocks, the mice may have consumed a lethal does and not be able to get out of your apartment to die, I would remove all rodenticides and use rat size glue traps, you will catch the mice faster and eradicate the infestation, tell the landord you need to have your apartment building rodent proofed to solve the problem once and all.