Bayern suffered another blow when Serge Gnabry sustained an Achilles injury during the mid-season training camp in Doha last weekend.
Gnabry joined the likes of prolific striker Robert Lewandowski and Kingsley Coman on a lengthy list of absentees.
Bayern head coach Hansi Flick has made it clear he wants to add to his depleted squad and defender Kimmich believes it is vital it brings in some new faces this month.
"At the training camp in Doha you can see that we've actually only got 12 or 13 professional players in the squad and the rest are youth," the Germany international said.
"The table for the youth players was full. That wasn't the case during my first year at Bayern.
"We might play until the end of the season in all three competitions and we have lots of international players too, so we need more players who are fit.
"Of course we have a lot of injured players. Gnabry couldn't train, Lewandowski and Coman will return soon.
"[Javi] Martinez also has a knock and [Niklas] Sule and [Lucas] Hernandez will take time. The club know that so they have to make a decision. At the moment, the squad is not big enough."
The Bundesliga champion is four points off the summit at the midway point this season and will return to league action with a trip to Hertha Berlin on 20 January.