Should I tell about my side hustle?

Hey guys,

I'm a recent Ivy-grad (bio major) and worked as a business analyst in the industry related to my startup, but was in non-competitive categories. I quit my job only after six months in because I needed to travel abroad for an extended period and work out the supply chain. It's been 6 months of unemployment, and my business is ready to launch in a couple of months. However, I'm contemplating on finding a 40hr/wk full-time job again for income and work until my business generates enough money to justify raising funds and/or at least a salary for myself, which may take a while.

If asked "Why did you leave your previous job?" or "What have you been doing during your employment?", I'm not sure if I should come clean or conceal my side business since while it'll be in the same industry, I'm deliberately avoiding companies with competitive categories.

Plan B is to just apply for a similar role in another industry. Concerned it'll be harder since I'm a pre-med turned business analyst and only worked for such a short time.

Appreciate any input or advice you guys can give. Thanks!