Definitely don't lie. When you start studying pharmacy they have you stick to the GPHC principles of professional conduct, and the first one is being honest and trustworthy. If you tell them you went for a week and learnt loads of things they'll ask you about them and if they realise you've lied it won't go down well. I only had 3/4 days worth of work experience when I applied, other people didn't have any, and some had jobs in pharmacies beforehand but they definitely weren't in a majority. Don't worry, universities don't really expect it because it's fairly hard to get work experience before you leave school. Definitely don't worry, and don't lie.