Bit of advice for you. If you do go into work but don't have the ice and rest available to you then you will be going against specific medical advice. If your bite then becomes infected and a serious complication arises due to you not resting and applying ice you could be found negligent for not adhering to medical advice. RM could then sack you with no payout or sick pay due to being unable to work due to your own negligence. Or if you slip on the bus on the way into work due to a stiff leg and seriously break your leg making you incapable of working again you could also be found negligent. If you cause an accident in your car due to injuries to your leg and inability to control your pedals your could be sued.
Think HARD about ignoring doctors/NHS advice just to appease your manager.
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