The Disclosure and Barring Service will only issue an order barring from someone from working with vulnerable adults if they've been convicted of a relevant serious offence (such as a sexual assault). That clearly doesn't apply to you.
Other than that though, it's entirely at an individual employer's discretion as to whether or not to employ someone whose Standard or Enhanced DBS check shows that they've fallen foul of the law at some point in their life.
However you shouldn't need to worry about it anyway. A caution for an offence committed over 6 years ago is now 'protected' and will therefore be 'filtered' from a DBS check. (That rule doesn't apply to certain 'specified' offences, such as sexual ones, but the only 'specified' offence under The Control of Drugs Act is that of supplying drugs to children, which doesn't apply to you).
So, unless you've had any other brushes with the law, your DBS check shouldn't show anything untoward anyway.
https://www.gov.uk/government/publications/dbs-filtering-guidance/dbs-filtering-guide