My Chain has started to jump off the lower cog, but it’s only happening on the small chain ring. Not sure why this is all of a sudden happing? Could this be an indicator that I need a new chain?
Jumping down or jumping up? Different problems, different fixes.
Also, small chain ring/smallest cog is not a gear combination you should ride in too much (if at all). Lots of chain flex there which causes chain/cog/chain ring wear issues.
the cables off your front derailleur may have stretched or the front derailleur simply needs adjustment that’s all …
basic bike maintenance 
All the time or only when your applying force?
Hanger bent?
Kink in rear dearilluer cable housing loop?
Cable’s have stretched. Simple rear derailluer adjustment will fix… $9.95 @ my LBS or do it your self
Agree with Tri_Bi, small chain ring and smallest cog’s shouldn’t really be ridden in.
Jumping down or jumping up? Different problems, different fixes.
Sorry - I did a poor job of explaining. The chain is jumping *off *the lower cog of the deraileur. As I look at the chain/cog from behind the chain is ridding on the edge of of the lower deraileur cog. I can still pedal - but it makes a lot of noise.
Ahem, that’s Tri_Bri (with 2 “Rs”), not Tri_Bi–don’t wan’t to be giving anyone the wrong impression. I’m not a switchhitter.
I’m no wrench, but I’d guess maybe a bent derailluer cage? If the chain is riding correctly on the upper jockey wheel, but on the outside of the lower jockey wheel, then maybe the cage got bent inward somehow (bike dropped/some one backed into bike while it was on bike rack?).
It is possible you bent your der. hanger that the der. is mounted to on your frame. Easy fix for a bike shop. Could also be your der. is bent.