Honestly I wouldn't worry to much at the moment...he's still very little.
It takes some time for them to get used to the new tastes, I've read conflicting opinions that it can take between 3 and 17
times of trying a new taste before a LO will accept it/like it.
The general advice for starting solids is that you give one new thing every 3 or 4 days, I believe - so that they get used to the flavours and so that you can see if they have any kind of reaction to it.
FWIW Ben never particularly enjoyed single veg puree - once he had been on solids for a while I started to mix them up a bit (say carrot, potato and parsnip), he still won't eat avocado but loves pasta with courgette and tomatoes (and sweet potato curry, and casserole and...well - he is a bit of a food monster!).
Don't forget that your LO still gets nearly all of his nutrition from his milk at the moment, so it's really just about introducing new flavours and getting him used to using his tongue to push food to the back of his mouth and then swallowing.
Once he gets a bit bigger and is on more solids I have also read (can't remember if it was in BW or not) that each meal should consist of a savoury and then a sweet (fruit, yoghurt etc...) course anyway, so they don't see getting the 'sweet' as a reward for eating savoury, but it gives them a more rounded diet.