Have you tried connecting headphones to check that it is a speaker problem and not a left channel audio problem?
If it is a speaker problem, here’s a link to the service manual for your laptop, taken from this webpage.
Scroll to p.60 to view the necessary pre-requisite steps and then the procedure to remove/ replace the speakers.
Replacement speakers are available online. Just search for Dell Inspiron 15 gaming 7567 speaker part to get results for suppliers.
Here’s a link to just one supplier. It is shown only to give you an idea of the cost of the parts. There are other that may suit you better.