I need to test some signals off. I use Debian and need to inject packets which the broadcom chipset inside this would not allow or maybe I don't know how to ( I mean, if I run "wash" tool it doesn't provide me any results and gave some kind of error, which on googling seemed to be the "packet injection inability".). So, is there any ways I can solve this?
For packet injection abilities you have to buy a wifi chipset that does support the functionality; Broadcom is not certainly one of them.
Some chipsets support monitor mode, and even a stricter small set does support injection capabilities; shame is that in several ethical hacking courses, that limitation is not mentioned.
You will have better results with a few Atheros chipset cards, search/Google around for a good USB pen. It won't came cheap, but it is worth every penny.
Beware of buying internal Wifi replacements for your notebook, as a few brands do hardware whitelisting (Lenovo, Dell, HP, Compaq) and if not bought directly to the brand for the specific notebook model, the equipment will reject it. (I have already noticed it is a Mac -- go with the USB pen).
see related thread Wi-Fi problems using ASUS USB-N13 adapter